On the 11th anniversary of 9/11, 75 chorus students from a Miramar elementary school showed up at a local Walmart, while wearing red, white and blue attire, to sing "God Bless America" as part of a prearranged tribute...until a Walmart representative refused to honor an agreement to allow the kids to sing inside the store, according to their school's principal, reports the South Florida Sun-Sentinel.

The performance was a part of a school-related "I Will" campaign, which encourages folks to help a stranger and do a public service on 9/11, according to the principal.

School staff and parents then led the singers outside the store, where they gathered under a nearby flag that was at half-staff and sang "God Bless America."

That's when cops then showed up in response to a report of a "flash mob situation."

Wednesday evening a Walmart spokeswoman apologized and said the store is "inviting the kids back to the store to help honor the victims and fallen heroes."